Human infants have a much larger portion of brown adipose tissue than adult humans. It was found that the mitochondria in brown adipocytes (brown fat cells) have a novel protein in the inner mitochondrial membrane
This protein, called the uncoupling protein (UCP), was found to transport protons from the intermembrane space into the matrix.
A. What is the impact of UCP on oxidative phosphorylation in the mitochondria of brown fat?
B. Propose an explanation for the higher proportion of brown fat cells in infants compared to adults.
A. A protein that transports protons into the mitochondrial matrix would diminish the proton gradient. Without the proton gradient, ATP will not be generated. However, the electron-transport chain can still work, as long as oxygen is present. The UCP, therefore, is a biological uncoupler of the oxidative phosphorylation process. The electron-transport chain will run in a futile cycle that does not convert the energy from redox reactions into chemical energy (ATP), but instead releases this energy as heat.
B. The thermogenesis resulting from the action of UCP is important for helping infants maintain a constant body temperature. As our body mass increases with age, our body temperatures are probably less susceptible to fluctuations, and therefore adults do not require the same amount of brown fat as infants.
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